The team was taking stabs in the dark — it didn’t know whether the two primates had the same blood type, whether the transfusion would work or whether Mumbali would even survive the ordeal.

Mumbali’s story, along with countless others, reveals the lack of data on great ape blood types. But researchers and veterinarians are catching on, as they assist captive primates much in the same way humans help one another — with blood banks.

After Mumbali’s primitive last-minute transfusion, Kathryn Gamble and Jill Moyse started opportunistically drawing blood from other great apes at the Lincoln Park Zoo when the animals were anesthetized during routine checkups.

Last September, the same team announced it had created a project to study the blood types of great apes in captivity. Incorporating this science into animals’ Species Survival Plans, zoos around the world have provided data on roughly 680 captive bonobos, chimpanzees, gorillas and orangutans.

These efforts highlight a conclusion long suspected, but never explored in its entirety: the striking similarities between human and nonhuman primate blood.

Like humans, apes have distinct immune antigens called agglutinogens on the surface of red blood cells. Blood is not interchangeable between humans and primates, but apes still possess a diversity of blood types similar to humans, including A, B, AB and O. Essentially, this means that some primates have a specific agglutinogen on the surface of the cell, while others have a mixture of A and B or no antigens at all (O type). Because some people and nonhuman primates possess red blood cells with no antigens, their blood is less likely to be rejected by another animal’s immune system, even if that animal has a different blood type.

When vets perform a blood transfusion with little knowledge of the donor and recipient’s blood type, the procedure can end tragically. If there’s no match, the recipient’s immune system will launch an attack on the foreign cells, which will cause the blood to clot and limit the flow of the vital oxygen needed throughout the body.

So far, scientists know that bonobos have Type A blood, whereas orangutans express a range of A, B, AB and O. Unfortunately, genetic sequencing cannot reliably characterize the blood types of gorillas at this time. This type of work isn’t new, but has mostly been limited to species of primates used for biomedical research — such as the rhesus macaque.

The project’s emphasis on collating blood data for the health of the animals, not necessarily humans, makes it unique and heartfelt. As of 2010, approximately half of the primate species in the world faced extinction, according to an International Union for the Conservation of Nature report. It’s clear that ensuring the health and stability of captive populations is necessary for the species’ survival in the long-run.

Losing apes from illnesses — both environmentally-induced and congenital — is not unusual in captivity or in the wild.